Optical source with passive pulse shaping
View Patent ↗The invention relates to sources of sub-picosecond optical pulses based on single-pass or double-pass optical amplifiers with an optical gain bandwidth in the 2-20 nm range. A passive pulse shaping filter is provided in front of the optical amplifier for pre-shaping seed optical pulses so as to passively pre-compensate for the gain narrowing effect in the optical amplifier. The passive pulse shaping filter may be based on a reflective thin film filter, which may be coupled to a mirror in a multi-pass configuration.
1. An optical pulse source comprising:
a seed optical source configured to generate a seed optical pulse of a sub-picosecond duration;
a pulse shaping filter configured to receive the seed optical pulse and broaden, prior to amplification of the seed optical pulse, the seed optical pulse in spectrum to pre-compensate for a gain narrowing effect associated with the amplification; and
an optical amplifier, including a gain element providing a gain spectrum, configured to amplify the broadened seed optical pulse,
where a number of passes through, or reflections from, the pulse shaping filter by the seed optical pulse exceeds a number of passes through the optical amplifier by the broadened seed optical pulse.
2. The optical pulse source of claim 1 , where the pulse shaping filter is a notch filter.
3. The optical pulse source of claim 2 , where the notch filter has a notch center wavelength aligned with a wavelength gain peak of the optical amplifier.
4. The optical pulse source of claim 1 , where the pulse shaping filter has a notch that has a width of 2-6 nm.
5. The optical pulse source of claim 1 , where the gain element comprises Yb doped material.
6. The optical pulse source of claim 1 , where
the gain element provides a gain magnitude of at least 3 dB and a gain bandwidth of less than 20 nanometers, and
the gain spectrum is a bell-like gain spectrum.
7. The optical pulse source of claim 1 , where the pulse shaping filter has a notch that has a depth of 10-30% of a maximum transmission of the pulse shaping filter.
8. The optical pulse source of claim 1 , where the pulse shaping filter includes a stack of thin film layers disposed on a reflective surface.
9. The optical pulse source of claim 1 , where the pulse shaping filter includes a stack of thin film layers disposed on a transparent surface.
10. A method comprising:
generating, by a seed optical source, a seed optical pulse of a sub-picosecond duration;
receiving, by a pulse shaping filter that includes a stack of thin film layers disposed on a reflective surface, the seed optical pulse;
broadening, by the pulse shaping filter and prior to amplification of the seed optical pulse, the seed optical pulse in spectrum to pre-compensate for a gain narrowing effect associated with the amplification; and
amplifying, by an optical amplifier including a gain element providing a gain spectrum, the broadened seed optical pulse.
11. The method of claim 10 , further comprising:
reducing, using a notch associated with the pulse shaping filter, a gain narrowing effect of the optical amplifier.
12. The method of claim 10 , where the gain element comprises Yb doped material.
13. The method of claim 10 , the gain element provides a gain magnitude of at least 3 dB and a gain bandwidth of less than 20 nanometers, and
the gain spectrum is a bell-like gain spectrum.
14. The method of claim 10 , where a quantity of times that the seed optical pulse is transmitted through, or reflected by, the pulse shaping filter exceeds a quantity of times that the seed optical pulse is transmitted through the gain element.
15. A device comprising:
a notch filter configured to:
receive a seed optical pulse of a sub-picosecond duration from a seed optical source; and
broaden, prior to amplification of the seed optical pulse by an optical amplifier, the seed optical pulse in spectrum to pre-compensate for a gain narrowing effect associated with the amplification.
16. The device of claim 15 , where the notch filter includes a minimum value, associated with a transmission characteristic, at a particular wavelength.
17. The device of claim 16 , where the particular wavelength is substantially equal to a central wavelength of a gain spectrum of the optical amplifier.
18. The device of claim 15 , where the notch filter includes a stack of thin film layers disposed on a reflective surface.
19. The device of claim 18 , where a depth and a width of the stack of thin film layers is selected based on information associated with a target range of pump power and amplification.
20. The device of claim 15 , where the notch filter is rotatable for aligning a particular wavelength thereof with a central wavelength of a gain spectrum of the optical amplifier.
21. The device of claim 15 , where a spectral width of the notch filter is approximately 20 nm.
22. The device of claim 15 , where the notch filter has at least one of:
a notch center wavelength aligned with a wavelength gain peak of the optical amplifier, or
a notch that has a width of 2-6 nm.
23. The device of claim 15 , where a number of passes through, or reflections from, the notch filter by the seed optical pulse exceeds a number of passes through the optical amplifier by the broadened seed optical pulse.